Feed-forward canceller

ABSTRACT

A feed-forward cancellation system includes a transmitting element and a receiving element. The transmitting element is in electrical communication with a transmitting line. The transmitting element is configured output a transmission signal to the transmitting line. The receiving element is in electrical communication with a receiving line. The receiving element is configured to process a response signal that is generated in response to the transmission signal and that is delivered to the receiving line. At least one antenna is configured to transmit the transmission signal, receive the response signal generated based on the transmission signal, and deliver the response signal to the receiving line. The feed-forward cancellation system further includes an electronic cancellation unit configured to generate a cancellation signal based on the transmission signal. The cancellation signal eliminates saturation from at least one of the response signal and the receiving line.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional of U.S. Provisional PatentApplication Ser. No. 61/908,373, filed Nov. 25, 2013, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND

The present disclosure relates to simultaneous transmission andreceiving systems.

Conventional systems capable of transmitting and receiving datasimultaneously will be subject to leakage and/or reflections. Theleakage and/or reflections can saturate the first gain stage in thereceive path. The saturation, however, prevents the system fromoperating properly.

SUMMARY

According to one embodiment, a feed-forward cancellation systemcomprises a transmitting element and a receiving element. Thetransmitting element is in electrical communication with a transmittingline and configured to output a transmission signal to the transmittingline. The receiving element is in electrical communication with areceiving line. The receiving element is configured to process aresponse signal that is generated in response to the transmission signaland that is delivered to the receiving line. At least one antenna isconfigured to transmit the transmission signal, receive the responsesignal generated based on the transmission signal, and deliver theresponse signal to the receiving line. The feed-forward cancellationsystem further includes an electronic cancellation unit configured togenerate a cancellation signal based on the transmission signal thateliminates saturation from at least one of the response signal and thereceiving line.

According to another embodiment a method of eliminating saturation in asimultaneous transmitting and receiving system comprises delivering atransmission signal from the simultaneous transmitting and receivingsystem to at least one antenna. The method further comprises receivingvia the at least one antenna a response signal that is based on thetransmission signal and delivering the response signal to a receivingline of the simultaneous transmitting and receiving system. The methodfurther comprises generating a cancellation signal based on thetransmission signal using the simultaneous transmitting and receivingsystem. The cancellation signal is configured to eliminate saturationfrom at least one of the response signal and the receiving line.

Additional features are realized through the techniques of the presentdisclosure. Other exemplary embodiments are described in detail hereinand are considered a part of the claimed invention. For a betterunderstanding of the various exemplary embodiments, the followingdescription is provided.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts:

FIG. 1 is a schematic diagram generally illustrating a feed-forwardsystem according to an exemplary embodiment of the present disclosure;

FIG. 2 is a schematic diagram illustrating a frequency domainchannelized active RF cancellation architecture for wideband signalsaccording to an exemplary embodiment;

FIG. 3 is a schematic diagram illustrating a signal flow through thefrequency domain channelized active RF cancellation architecture forwideband signals according to an exemplary embodiment;

FIG. 4 is a schematic diagram illustrating a time domain feed-forwardcancellation system according to at least one exemplary embodiment;

FIG. 5 is a schematic diagram illustrating a feed-forward cancellationsystem comprising a cancellation unit including an electronic digitalsignal processor capable of replicating a leakage and/or interferencesignal;

FIG. 6 is a schematic diagram illustrating a feed-forward cancellationsystem comprising a cancellation unit including an electronic digitalsignal processor and a signal detector capable of identifying one ormore types of saturation;

FIG. 7 is a schematic diagram generally illustrating a dual antennafeed-forward cancellation system according to an exemplary embodiment;

FIG. 8 is a schematic diagram illustrating a dual antenna feed-forwardcancellation system in greater detail according to an exemplaryembodiment;

FIG. 9 is a schematic diagram illustrating a dual antenna feed-forwardcancellation system according to another exemplary embodiment;

FIG. 10 is a schematic diagram illustrating a dual antenna feed-forwardcancellation system according to yet another exemplary embodiment;

FIG. 11 is a flow diagram illustrating a method of eliminatingsaturation in a simultaneous transmitting and receiving system accordingto an exemplary embodiment;

FIG. 12 is a flow diagram illustrating a method of eliminatingsaturation in a simultaneous transmitting and receiving system accordingto another exemplary embodiment; and

FIG. 13 is a flow diagram illustrating a method of eliminatingsaturation in a simultaneous transmitting and receiving system accordingto yet another exemplary embodiment.

DETAILED DESCRIPTION

At least one embodiment of the disclosure provides a feed-forwardcancellation system that is configured to mitigate reflection and/orleakage in a simultaneous transmission and receiving system, forexample. The same system can also mitigate Radio Frequency Interference(RFI) from external sources including the environment and jammers. Thefeed-forward cancellation system comprises a frequency domain centricsystem, a time domain centric system, or a combination of a frequencydomain and time domain centric system to cancel interference and leakagesignals as they enter the receiving portion of the system. Theinterference signals include, but are not limited to, self-inflictedwideband interference signals and interference signals. Accordingly,saturation of all receive stages, including the Analog to DigitalConverter (ADC), are prevented. If linearity is maintained from the RFfront-end through the digitizing process, then the digital signalprocessing (DSP) end of the system can remove the interference residuewith high levels of precision.

Referring to FIG. 1, a feed-forward cancellation system 10 transmits anoriginal signal on a transmission line 12 to an antenna 14, andmitigates and/or cancels one or more reflected signals received on areceiving line 16. In at least one embodiment, an incoming receivedsignal present at the receiving port of a circulator 18 is similar tothe transmitted signal from the system 10 due to one or more signalreflections and/or signal leakage. Various reflected and/or leakagesignals are canceled by the feed-forward cancellation system 10. Forexample, the feed-forward cancellation system 10 cancels leakage signals20, antenna reflection signals 22, and interference signals 24. Theleakage signals 20 include, for example, a portion of the originaltransmission signal that leaks through the circulator 18 and onto thereceiving line 16. The antenna reflection signals 22 include signalsthat are reflected back from the antenna 14. The interference signals 24include reflected signals 26 received by the receiving line 16 that arereflected from the external environment. The external environmentincludes, but is not limited to, mountainous terrain, aircraft, navalvessels and land vehicles.

At least one exemplary embodiment of a feed-forward cancellation system10 according to the present disclosure includes a cancellation unit 106configured to split a wide-band transmission signal into a plurality ofsub-band signals. The cancellation unit 106 is interposed between thetransmission line 12 and the receiving line 16 as further illustrated inFIG. 1. According to an embodiment, the split sub-bands are equal to oneanother. Each sub-band signal is delivered to a respective band passfilter which feeds the channels of a signal canceller. Each channel usesa feedback loop fed by the post cancelled signal to optimize the signalcancellation. Each channel includes, for example, a tunable RF delay andamplitude circuit which is controlled by a digital controller.

Referring to FIG. 2, for example, a frequency domain feed-forwardcancellation system 100 is illustrated according to at least oneexemplary embodiment. The frequency domain feed-forward cancellationsystem 100 includes a transmitting element 102, a receiving element 104,a cancellation unit 106, a circulator 108, a canceller microcontroller110, and a signal detector 112. The transmitting element 102 includes apower amplifier (PA), which outputs a transmission signal to atransmission line/radiator to transmission path 114. The receivingelement 104 includes a low noise amplifier (LNA), which receives atransmission signal from transmission path 114. The cancellation unit106 is communicatively interposed between the transmitting element 102and the receiving element 104. In this regard, the cancellation unit 106cancels leakage of the transmission signal through the circulator 108before the leakage is fed to the receiving element 104. As a result, asignal received from free space excluding leakage is provided. Thecancellation unit 106 also cancels reflections of the free spacetransmission signal received from free space before the transmissionsignal is fed into the receiving element 104.

According to at least one exemplary embodiment, the cancellation unit106 is configured as a channelized canceller 106. The channelizedcanceller 106 includes one or more filter elements 116 and one or morerespective tunable cancellation elements (TCE) 118 configured toactively cancel reflections in a transmission signal received fromtransmission path 114 before the transmission signal is received by thereceiving element 104. According to at least one embodiment illustratedin FIG. 2, the channel canceller 106 includes a low pass filter (LPF)116 a, a mid pass filter (MPF) 116 b, and a high pass filter (HPF) 116c. It is appreciated that the combination of filter elements 116 is notlimited thereto. The channelized canceller 106 is configured to processbroad frequency bandwidths and/or systems with mismatched components.For example, an active cancellation process and a sub-banding process tomitigate reflection are performed immediately upon receiving the signalfrom free-space. The channelized canceller 106 first splits the transmitsignal into one or more frequency bands to ease the cancellationrequirements. This allows wider bandwidths to be addressed withoutsuffering degradation at the bands edges. This concept can be expandedto include more than three frequency bands depending on mitigationrequirements and system characteristics.

A respective TCE 118 is interposed between each filter 116 and thereceiving element 104. The feed-forward cancellation system, (e.g.,active cancellation and sub-banding), therefore, operates on thetransmission signal received from transmission path 114 before thesignal is fed to the receiving element 104. According to at least oneembodiment, each TCE 118 has different frequency response settings withrespect to one another. For example, a first TCE 118 connected to theLPF has a frequency response setting with a different slope or transferfunction than the mid or high portions of the signal. A second TCE 118connected to the MPF has a frequency response with a differentcharacteristic. Thus, each TCE 118 is able to optimize the matching ofthe transmission signal frequency response in order to most effectivelycancel it.

The circulator 108 is communicatively coupled to an antenna 120 (e.g., ablade antenna), via a transmission path 114. The transmission path 114has a length (L). The circulator 108 receives reflections back from theantenna 120 due to mismatches in both the transmitting and receivinglines. The canceller microcontroller 110 is configured to control one ormore of the TCEs 118 to actively tune a respective channel. The signaldetector 112 (hereinafter referred to as detector 112) has an inputinterposed between the circulator 108 and the receiving element 104, forexample, and an output that is connected to the cancellermicrocontroller 110. The characteristics of the transmission signal(e.g., reflections, leakage, voltage level, frequency, etc.) travelingon the receiving line is therefore detected before being fed into thereceiving element 104, and before being provided to the cancellermicrocontroller 110. The canceller microcontroller 110 thereforedynamically controls one or more TCEs 118 to actively remove undesiredsignals before the undesired signals are input to the LNA 104, forexample. Although the frequency domain cancellation system 100 isillustrated as an active cancellation system 100, it is appreciated thatthe canceller microcontroller 110 can be omitted to provide a passivefrequency domain cancellation system.

Referring to FIG. 3, a signal view of the system 100 is illustratedaccording to at least one embodiment. During normal leakage mitigation,an original signal (S1) is generated by the system 100 and is amplifiedby the transmitting element 102. A small portion of S1 is diverted tothe channelized canceller 106 where it is processed by the TCEs tocancel the leakage. The remaining portion of S1 is sent out to thetransmission path/radiator 114, where it is transmitted over free space.A portion (S1 leakage) of the original transmission signal S1 leaksthrough the circulator 108 and on to the receiving line. This unwantedleakage is cancelled using the S1 sample processed by the channelizedcanceller 106. Similarly, a portion (S1 reflected) of S1 also reflectsoff of the antenna 120 as the original transmission signal S1 travelsthrough free space. The reflected signal is also cancelled using theoutput of the channelized canceller 106. Cancelling the S1 leakageand/or the S1 reflected signals allows the system 100 to better detectthe received signal of interest (RSOI) by removing the saturation (i.e.,the S1 leakage and/or S1 dreflected signals) or reducing the saturationto low residual levels.

It is also possible for the frequency domain approach to be applied to asystem (such as a Digital RF Memory—DRFM system) which is capable ofsynthesizing a received wideband pulse or an a priori frequency responseand using the active channelized canceller to mitigate wideband RFinterference received from external sources.

Referring to FIG. 4, the system 100′ is illustrated according to anotherembodiment. The system 100′ illustrated in FIG. 4 is configured as atime domain feed-forward cancellation system 100′. The time domainfeed-forward cancellation system 100′ includes a transmitting element102, a splitter 103, a receiving element 104, a cancellation unit 106′,a combiner 107, a circulator 108, a canceller microcontroller 110, and adetector 112. The transmitting element 102 includes a power amplifier(PA), for example. The transmitting element 102 outputs a transmissionsignal to transmission path 114 that is in electrical communication withan antenna 120. The receiving element 104 includes a low noise amplifier(LNA), for example. The receiving element 104 receives a transmittedsignal transmitted from the antenna 120 via the transmission path 114.

The cancellation unit 106′ is interposed between the splitter 103 andthe combiner 107. In this regard, the cancellation unit 106′ cancelsleakage of the transmission signal through the circulator 108 before theleakage is fed to the receiving element 104. As a result, a signalreceived from free space excluding leakage is processed at the receiverside of the system 100′. The cancellation unit 106′ can also cancelundesired reflections of the free space transmission signal before thetransmission signal is fed into the receiving element 104. According toat least one exemplary embodiment, the signal output from thetransmitting element 102 is split out by delay lengths based on theprimary reflection paths back to the receivers. Multiple mitigationpaths with differing time delays provide cancellation from interferencesignals separated in time, mainly due to the transmission path betweenthe circulator 108 and the antenna 120. These paths include: leakagedirectly through the circulator to the receiver; reflections from theantenna back to the receiver; reflections from the antenna that reflectback from the circulator, and which reflect again off of the antennaback to the receiver; reflections from the aircraft structure back tothe receiver; reflections from the ground back to the receiver;

As illustrated further in FIG. 4, at least one embodiment couples off(i.e., diverts) a small amount of the transmitted signal to the splitter103. The splitter 103 splits the diverted signal into a plurality ofsub-signals. Each sub-signal is delivered to a respective cancellationpath 200 of the cancellation unit 106′. Each cancellation path 200includes a variable attenuator 202, an electronic antenna modelingcontrol unit (i.e., an antenna modeler) 204, and an electronicphase/amplitude shifter 206. The cancellation unit 106′ controls a timedelay corresponding to a respective path 200. According to at least oneembodiment, each path 200 has a different time delay associated with it.The delay of each of the paths 200 corresponds with the time it takesfor the signal to reflect off of various fixed reflection points in thefeed-forward cancellation system 100′ as described above. Each path 200associated with reflections from the antenna 120 also includes a networkhaving forward transfer characteristic that match the reflectioncharacteristic of the antenna 120. The phase/amplitude shifter 206inverts the diverted signal to create a cancellation signal that is 180degrees out of phase with respect to the leaked signal and/or reflectedsignal. The phase/amplitude shifter 206 also provides a fine adjustmentof attenuation and phase of the cancellation signal. The combiner 107combines all the paths 200 and delivers the combined signals from eachof the paths 200 back on to the receive path of the feed-forwardcancellation system 100′. Accordingly, the cancellation signal cancelsthe leaked signal and/or reflected signal existing on the receive pathprior to delivering the signal traveling on the received path to thereceiving element 104. Thus, each path 200 is selectively tuned suchthat when cancellation signals output from a respective path 200 arecombined with the reflected signal existing on the receiving line, thereflected signals are cancelled.

Although not illustrated, it is appreciated that the feed-forwardcancellation system 100′ described above can be combined with theembodiments shown in FIGS. 1-3. For example, one or more of the paths200 connected to the splitter 103 are replaced with a cancellation unit106 illustrated in FIGS. 1-3. In this regard, reflections occurring atparticular time placements are removed using the cancelation system106′, while reflections caused by a wideband signal are removed usingthe cancellation unit 106. According to an exemplary embodiment, if theinterference is self-inflicted reflection and/or leakage, then theoriginal signal output from the transmitting element 102 determineswhether a frequency cancellation approach or a time domain approachshould be performed. According to another exemplary embodiment, if theinterference is external, a radio frequency interference (RFI)cancellation is performed based on the bandwidth of the interferingsignal.

Another embodiment of the feed-forward cancellation system is providedwhere the cancellation unit includes an electronic digital signalprocessor capable of replicating a leakage and/or interference signalthat is expected to appear the receiving line. The digital signalprocessor generates the replicated signal in addition to the system'sown operating signal, and uses the replicated signal to cancel theleakage and/or interference signals. According to at least one exemplaryembodiment, the system's own signal of interest could be preserved whilethe RFI is mitigated.

Referring to FIG. 5, for example, a feed-forward cancellation system100″ includes a transmitting element 102, a receiving element 104, acancellation unit 106″, and a circulator 108. The transmitting element102 includes a power amplifier (PA), which outputs a transmission signal109 to a transmitting line 111. The transmitting line 111 is inelectrical communication with a transmission path 114. The transmissionpath 114 electrically communicates with an antenna 120 over free-space,for example. The receiving element 104 includes a low noise amplifier(LNA) 104. The LNA 104 is configured to receive a signal 113, e.g., aresponse signal 113, provided by an antenna 120, which is delivered to areceiving line 115 via a circulator 108.

The cancellation unit 106″ includes an electronic digital signalprocessor (DSP) 300 and a signal combiner 302. The DSP 300 includes afirst output that is in electrical communication with the transmittingline 111, and a second output that is in the electrical communicationwith the receiving line 115 via the signal combiner 302. The DSP 300generates a transmission signal 109 that is delivered to thetransmitting line 111. The transmission signal 109 is amplified by thefirst power amplifier 102 before being delivered to the transmittingline 111. The amplified transmission signal 109 is then transmitted tothe antenna 120 via the circulator 108. The DSP 300 also generates acancellation signal 304 that is delivered to the receiving line 115.Since the DSP 300 is aware of the transmission signal 109 to begenerated, the cancellation signal 304 is generated with a phase that isshifted 180 degrees with respect to the transmission signal 109.According to an embodiment, the cancellation signal 304 is generatedsimultaneously with the transmission signal 109, or even prior togenerating the transmission signal 109. In this regard, at least oneexemplary embodiment provides a feature where the phase-shiftedcancellation signal 304 cancels a portion of the transmission signal 109that leaks through the circulator 108 and onto the receiving line 115.Since the DSP 300 is aware of the of the magnitude of the transmissionsignal 109, the DSP 300 may generate the cancellation signal 304 to havea magnitude that matches or is similar to the transmission signal 109.As a result, saturation on the receiving line 115 and/or saturation ofthe received signal 113 are eliminated.

Furthermore, the DSP 300 included in the embodiment of FIG. 5 eliminatesthe need for a channelized canceller. Since the DSP 300 is aware of thetransmission signal 109 and simultaneously generates a cancellationsignal 304 having a shifted phase, there is no need to include achannelized canceller for splitting a portion of the transmitted signal109 and generating a cancellation signal based on the split signal.Since the transmission signal 109 is not split, the power amplificationon the input line is maintained at a desired power level therebyimproving the overall power efficiency of the feed-forward cancellationsystem 100″.

Referring to FIG. 6, a feed-forward cancellation system 100′″ isillustrated according to another exemplary embodiment. The feed-forwardcancellation system 100′″ operates similar to the feed-forwardcancellation system 100″ as described in FIG. 5. The DSP 300, however,further includes an input in electrical communication with a detector112. The detector 112 has an input in electrical communication with thereceiving line 115 to form a sample signal path 308, and an output thatis connected to an input of the DSP 300. The characteristics (e.g.,reflections, leakage, noise, voltage level, frequency, etc.) of thereceived signal 113 traveling on the receiving line 115 is analyzed bythe detector 112 via the sample signal delivered by the sample signalpath 308. The detector 112 determines if the receiving line 115 issaturated (i.e., determines one or more leakage signals 20, antennareflection signals 22, and/or interference signals 24) and generates anidentification signal 310 to the DSP 300 indicating the type ofsaturation that exists. Accordingly, the DSP 300 receives theidentification signal 310 and generates one or more cancellation signals304 that are delivered to the receiving line 115. The cancellationsignal 304 has a phase that is shifted 180 degrees with respect to theidentified saturation (i.e., leakage signals 20, antenna reflectionsignals 22, and/or interference signals 24), thereby cancelling thesaturation before the received signal 113 is delivered to the receivingelement 104. The feed-forward cancellation system 100′″ dynamicallygenerates one or more types of cancellation signals 304 based on thedetected saturation to actively improve the quality of the receivingline 115.

Still referring to FIG. 6, the DSP 300 is configured to identify asaturation signal (i.e., leakage signal 20, antenna reflection signal22, and/or interference signal 24). According to an embodiment, the DSP300 stores one or signal models of the saturation signal in memory, andcompares the sample signal to the stored models to identify thesaturation signal as, for example, a leakage signal 20, an antennareflection signal 22, and/or interference signal 24. The DSP 300 thengenerates a cancellation signal 304 that selectively cancels one or moreof the leakage signal 20, antenna reflection signal 22, and/orinterference signal 24, while maintaining one or more of the remainingsaturation signals. For example, the DSP 300 generates a cancellationsignal that cancels the leakage signal 20 and the antenna reflectionsignal 22, while maintaining the signal 24 on the receiving line 115. Inthis regard, the leakage signal 20, antenna reflection signal 22, and/orinterference signal 24 are independently identified and cancelledindependently with respect to one another.

Although various embodiments described above include a single antennaconfigured to operate as both a transmitting antenna and a receivingantenna, some electronic systems operate according to very high powerconditions. Consequently, a single antenna does not achieve adequateisolation. Therefore, another exemplary embodiment of a feed-forwardcancelation system 100″″ illustrated in FIG. 7 is configured as a dualantenna system 400 that includes a first antenna 120 (e.g., atransmitting antenna 120) connected to a transmitting line 111, aseparate second antenna 120′ (e.g., a receiving antenna 120′) connectedto a receiving line 115, and a cancellation unit 106″″ electricallyinterposed between the first transmitting line 111 and the secondreceiving line 115. The first antenna 120 and the second antenna 120′are located remotely from one another by distance of, for example,approximately 3-6 feet (ft.).

The feed-forward cancellation system 100″″ is configured to couple off aportion of the transmit signal transmitted to the receiving antenna120′. The coupled signal 402 is fed onto the receive path. According toat least one embodiment, the coupled signal 402 is phase shifted withrespect to the transmit signal. In this case, the reflections leakagesignals 20 and the antenna reflection signals 22 do not apply to thefeed-forward cancellation system 100″″. However, one or more reflectionsignals 404 from the mutual coupling between the transmitting antenna120 and receiving antenna 120′ occurs. For example, the receivingantenna 120′ still receives a very large signal from the transmittingantenna 120 that is located a close proximity away. Here, theunclassified power level assumptions are a transmit signal ofapproximately 60 power decibels (dBm) to approximately 80 dBm, forexample. The signal is attenuated −60 dBm due to the physical separationbetween the transmitting antenna 120 and the receive antenna 120′. Theattenuation results in a signal of 0 dBm to 20 dBm, for example, thatpropagates along a leakage path formed between the transmitting antenna120 and receiving antenna 120′. The attenuated signal, i.e., thereflected/leaked signal 404, is received on the receive line 115 therebysaturating the receiving line 115 and/or the response signal deliveredto the receiving line 115. However, the cancellation unit 106″″ isconfigured to eliminate or reduce the reflected/leaked signal 404 signalfrom the receiving line 115. In this regard, the performance of thefeed-forward cancellation system 100″″ is improved in response toeliminating the saturation, i.e., the reflected/leaked signal.

Turning now to FIG. 8, a feed-forward cancelation system 100″″ includinga dual-antenna system 400 according to an exemplary embodiment isillustrated in greater detail. The feed-forward cancelation system100′″″ includes a first antenna (i.e., a transmitting antenna) 120connected to the transmitting line 111, a second antenna (i.e., areceiving antenna) 120′ connected to the receiving line 115, and acancellation unit 106. The cancelation unit 106″″ includes a DSP 300.The transmitting antenna 120 receives an original transmit signal 109from a DSP 300 via the transmitting line 111. In response to theoriginal signal 109, the transmitting antenna 120 communicates aresponse signal 402 to the receiving antenna 120′ as understood by thoseordinarily skilled in the art. However, a portion (i.e., an antennaleakage signal) 404 leaks between the transmitting antenna 120 and thereceiving antenna 120′. In this regard, a signal leakage pathway existsbetween the transmitting antenna 120 and the receiving antenna 120′. TheDSP 300 models the signal leakage pathway, and then utilizes the modelto generate a cancellation signal 304 in order to cancel the saturation,e.g., the antenna leakage signal 404.

As described in detail above, the DSP 300 determines one or more typesof saturation, such as the antenna leakage signal 404, which exists onthe receiving line 115. Based on the antenna leakage signal 404, the DSP300 generates a cancellation signal 304 that is added to the receivingline 115. The cancellation signal 304 has a phase that is shifted 180degrees with respect to the antenna leakage signal 404. Accordingly, thecancellation signal 304 cancels the antenna leakage signal 404 such thatthe receiving element 104 receives the response signal 402 transmittedfrom the transmitting antenna without realizing one or more types ofsaturation.

Referring to FIG. 9, a feed-forward cancellation system 100′″″ includinga dual-antenna system 400 is illustrated according to an exemplaryembodiment. The feed-forward cancelation system 100′″″ illustrated inFIG. 9 operates similarly to the feed-forward cancellation system 100″″illustrated in FIG. 8 to perform cancellation of saturation from thereceived signal 113. The sample signal path 308 and the combiner 302,however, are located downstream from the receiving element 104, butupstream from a second DSP 300′ that processes the received signal 113on the receiving side.

Still referring to FIG. 9, the cancellation unit 106″″ compares theoriginal transmitted signal 109 to the received signal 113 whichincludes the saturation, e.g., the leakage signal 404. Based on thecomparison, the cancellation unit 106″″ determines the linear distortionthat exists, and models the linear distortion according to a set ofcoefficients. In this regard, the cancellation unit 106″″ processes thecoefficients using various data processing systems including, but notlimited to, a Finite Impulse Response (FIR) filter system. A finiteimpulse response (FIR) filter (y) is modeled according to the followingequation:y(n)=Σ_(k=1) ^(M) b _(k) x(n−k),where ‘b’ represents the filter coefficients (weights), “k” representsthe term being iterated, x represents the input signal, and n representsthe filter order. The resulting output matches the leakage signal 404adjusting for linear distortions, and provides accurate parameters forgenerating a cancellation signal. The linear distortions include, butare not limited to amplitude, time delay, frequency dependentattenuation and filter effects, and multipath effects.

The cancellation unit 106″″ further utilizes various algorithmsincluding, but not limited to, a least mean squares (LMS) algorithm anda recursive least squares (RLS), each which allows for an ability toignore one or more signals that are uncorrelated to one or more types ofsaturation being analyzed e.g., the leakage signal 404. Accordingly, thecancellation unit 106″″ effectively removes saturation from thereceiving signal 113 even in the presence of other external signals. Byusing an LMS algorithm, for example, a distortion of the leakage path isdetermined and a real time adaptive system is provided to synthesize aduplicate signal for cancellation of the leakage signal.

Referring now to FIG. 10, a feed-forward cancellation system 100″″″including a dual-antenna feed-forward cancellation system 400 isillustrated according to an exemplary embodiment. The feed-forwardcancellation system 100″″″ illustrated in FIG. 10 operates similarly tothe feed-forward cancellation system 100′″″ illustrated in FIG. 9 tocancel saturation from the received signal 113. The feed-forwardcancellation system 100″″″ of FIG. 10, however, includes a cancelationunit 106′″″ configured as a leakage residue cancellation unit thatcancels residual leakage 408 that exists following initial cancellationof the saturation from the received signal 113 traveling on thereceiving line 115. One or more up/down converters are provided torespectively up-convert or down-convert the voltage of the system.

The leakage residue cancellation unit cancelation unit 106′″″ includesan electronic receiver digital signal processor (RDSP) 502 and anelectronic filter cancelling unit 504 configured to generate a timedelay when an RF signal is propagated along the delay line. Thefeed-forward cancelation system 100″″″ executes a dual-cancellationcalibration process that performs a first operation that cancels theoriginal saturation (i.e., the leakage signal 404 on the receiving line115 and a second operation that cancels the residual leakage 408 whichremains on the receiving line. Accordingly, a receiving signal 113′ thatexcludes the residual leakage 408 is generated.

In regards to the first cancellation operation, a transmitter DSP (TDSP)300 transmits a low-level calibration signal over the entire bandwidthof the transmitter antenna 120. The low-level calibration signal is, forexample, a stepped swept sinusoid where transmission signals are aconstant magnitude/phase. The phase ranges between 0 and 360 degrees.The RDSP 502 collects swept leakage data, and compares the receivedsignal 113 to the transmitted signal 109. The swept leakage data mayinclude, for example, two-dimensional (2D) array, magnitude and phasevs. frequency data. Based on the comparison, the RDSP 502 determines animpulse response of the system 100″″″. The impulse response iscalculated according various algorithms including, for example, aFourier transform algorithm as understood by those ordinarily skilled inthe art.

The filter cancelling unit 504 includes a programmable filter system,such as a programmable FIR filter system for example. The RDSP 502communicates with the filter cancelling unit 504, and programs thefilter cancelling unit 504 according to an inverted impulse response.Accordingly, the filter cancelling unit 504 cancels the leakage 404 atthe input of the receiving element 104. After cancelling the leakage 404at the initial transmitting signal level, the TDSP 300 increases thetransmitting signal level to a point where the leakage residue detectedby the RDSP 502 exceeds a predetermined level and determines anotherimpulse response at the increased transmitting signal level. Accordingto at least one embodiment, the RDSP 502 stores filter coefficients intwo-dimensional array of filter coefficients vs. RF level, andcontinuously repeats the process of determining the impulse responseuntil a complete dynamic range of system power is characterized.

With respect to the second operation, any residual leakage 408 of thesystem 100″″″ is characterized and canceled. More specifically, the TDSP300 determines the residual leakage 408 remaining after cancelling theoriginal saturation (e.g., the original leakage signal 404) on thereceiving line 115 for each of the RF levels and frequencies used toperform the calibration process described above. Thereafter, the RDSP502 determines swept residual leakage data to determine a residualleakage signal 408. The swept residual leakage data includes, forexample, two-dimensional (2D) array, magnitude and phase vs. frequencydata. The RDSP 502 compares the residual leakage signal 408 to theoriginal transmission signal 109 and determines an inverse Fouriertransform to yield the impulse response corresponding to the systemresidue leakage 408.

The RDSP 502 then communicates with the filter cancelling unit 504, andprograms the filter cancelling unit 504 according to an inverted impulseresponse of the system residue leakage 408. Accordingly, the residualleakage 408 is canceled from the RDSP 502 prior to any baseband signalprocessing/demodulation. In this regard, any baseband signalprocessing/demodulation components located downstream from the RDSP 502receive the received signal 113′, which excludes both the originalsaturation 404 (i.e., the original leakage signal 404) and the residualleakage 408.

Turning now to FIG. 11, a method for cancelling saturation from areceived signal traveling on a receiving line of a simultaneoustransmitting and receiving system is illustrated according to anexemplary embodiment. The method begins at operation 1000 and proceedsto operation 1002 to generate an original transmission (Tx) signal. Theoriginal Tx signal is delivered to a Tx path to be transmitted to anantenna. At operation 1004, the original Tx signal is split prior tobeing transmitted to the antenna. At operation 1006, a cancellationsignal is generated based on the split transmission signal. According toat least one exemplary embodiment, the phase of split signal is shiftedto generate the cancellation signal. At operation 1008, a received (Rx)signal generated by an antenna is received on a receiving line. The Rxsignal is also coupled with one or more types of saturation existing onthe receiving line. The saturation includes, but is not limited to,leakage signals, reflection signals, and interference signals. Atoperation 1010, the cancellation signal is combined with the Rx signalto cancel the saturation. Accordingly, an Rx signal excluding saturationis generated and the method ends at operation 1012.

Referring now to FIG. 12, a method for cancelling saturation from areceived signal traveling on a receiving line of a simultaneoustransmitting and receiving system is illustrated according to anotherexemplary embodiment. The method begins at operation 1100 and proceedsto operation 1102 to generate an original transmission (Tx) signal. Theoriginal Tx signal is delivered to a Tx path to be transmitted to anantenna. At operation 1104, a received (Rx) signal generated by anantenna is received on a receiving line. The Rx signal is coupled withone or more types of saturation existing on the receiving line. Atoperation 1106, the original Rx signal is split and the type ofsaturation (i.e., leakage signals, reflection signals, and interferencesignals) included with the original Rx signal is determined. Atoperation, 1108, a cancellation signal is generated based on thedetermined saturation. According to at least one exemplary embodiment,the phase of the cancellation signal is shifted 180 degrees with respectto the determined saturation. At operation 110, the cancellation signalis combined with the original Rx signal and the method ends at operation1112. Accordingly, an Rx signal excluding the determined saturation isgenerated.

Turning to FIG. 13, another method for cancelling saturation from areceived signal traveling on a receiving line of a simultaneoustransmitting and receiving system is illustrated according to anexemplary embodiment. The operation begins at operation 1200, and atoperation 1202 an original Tx signal to be transmitted to an antenna isdetermined. Based on the desired original Tx signal, a cancellationsignal is determined at operation 1204. At operation 1206, the originalTx signal and the cancellation signal are simultaneously generated.Accordingly, the original Tx signal is delivered to a Tx path beforebeing transmitted to an antenna and the cancellation signal is deliveredto an Rx path before receiving an Rx signal from an antenna. Accordingto at least one exemplary embodiment, the phase of the cancellationsignal is shifted based on the original Tx signal and/or a model of asignal leakage pathway. At operation 1208, an original Rx signal isreceived from an antenna and delivered to the Rx path. At operation1210, the original Rx signal is combined with the previously generatedcancellation signal delivered to the Rx path and the method ends atoperation 1212. Accordingly, any saturation coupled to the Rx signal isimmediately canceled.

As can be appreciated according to the various exemplary embodimentsdescribed in detail above, an original transmission signal is sampled tocancel one or more types of saturation that leak onto the receive lineand couple to the original received signal in RF applications. Bycancelling the saturation based on the sampling of the transmissionsignal, a more precise received signal is provided.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the various exemplary embodiments has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The exemplary embodiments were chosen to enable others of ordinary skillin the art to understand the invention for various embodiments withvarious modifications as are suited to the particular use contemplated.

While various exemplary embodiments have been described, it will beunderstood that those skilled in the art, both now and in the future,may make various modifications to the exemplary embodiments that fallwithin the scope of the claims which follow. These claims should beconstrued to maintain the proper protection for the invention firstdescribed.

What is claimed is:
 1. A feed-forward cancellation system, comprising: atransmitting element constructed as a high power amplifier that is inelectrical communication with a transmitting line, the high-powertransmitting element configured to output a high-power transmissionsignal to the transmitting line; a receiving element in electricalcommunication with a receiving line, the receiving element configured toprocess a high-power response signal that is generated in response tothe high-power transmission signal and delivered to the receiving line;at least one antenna configured to perform at least one of: transmit thehigh-power transmission signal, receive the high-power response signalgenerated based on the high-power transmission signal, and deliver thehigh-power response signal to the receiving line, wherein the at leastone antenna includes: a first antenna connected to the transmittingline; and a separate second antenna located remotely from the firstantenna and connected to the receiving line, the combination of thefirst and second antennas isolating the high-power transmission signalfrom the high-power response signal; an electronic cancellation unitinterposed between the first antenna and the second antenna, theelectronic cancellation unit including a digital signal processorconfigured to generate an electrical cancellation signal based on thehigh-power transmission signal, and injects the cancellation signalupstream from the receiving element so to eliminate saturation from atleast one of the high-power response signal and the receiving line,wherein the high-power transmission signal and the high-power responsesignal have a power level ranging from approximately 60 power decibels(dBm) to approximately 80 dBm.
 2. The feed-forward cancellation systemof claim 1, the digital signal processor is installed on a transmissionside of the feed-forward cancellation system, the DSP having a firstoutput that is in electrical communication with the transmitting line,and a second output that is in the electrical communication with thereceiving line.
 3. The feed-forward cancellation system of claim 1,wherein the cancellation signal is phase-shifted with respect to thehigh-power transmission signal.
 4. The feed-forward cancellation systemof claim 1, wherein the cancellation unit is configured to identify atype of saturation among a plurality of different saturation types, andto generate the cancellation signal in response to identifying the typeof saturation.
 5. The feed-forward cancellation system of claim 4,wherein the cancellation unit delivers the cancellation signal toreceiving line prior to outputting the high-power transmission signal.6. The feed-forward cancellation system of claim 5, wherein thecancellation signal is phase-shifted 180 degrees with respect to thehigh-power transmission signal.
 7. The feed-forward cancellation systemof claim 1, wherein the at least one antenna comprises: a transmittingantenna configured to receive the high-power transmission signal fromthe transmitting line; and a receiving antenna located remotely from thetransmitting antenna, the receiving antenna configured to receive theresponse signal and to deliver the response signal to the receivingline.
 8. The feed-forward cancellation system of claim 7, wherein theelectronic cancellation unit is configured to model a leakage pathexisting between the transmitting antenna and the receiving antenna, andto generate a digital cancellation signal based on the modeled leakagepath.
 9. A method of eliminating saturation in a simultaneoustransmitting and receiving system, the method comprising: delivering ahigh-power transmission signal from a high power amplifier included inthe simultaneous transmitting and receiving system to at least oneantenna; receiving via the at least one antenna a high-power responsesignal that is based on the high-power transmission signal, processingthe high-power response signal via a receiving element, and deliveringthe high-power response signal to a receiving line of the simultaneoustransmitting and receiving system, wherein the at least one antennaincludes: a first antenna connected to the transmitting line; a separatesecond antenna located remotely from the first antenna and connected tothe receiving line, the combination of the first and second antennasisolating the high-power transmission signal from the high-powerresponse signal; and generating a digital cancellation signal based onthe high-power transmission signal using the simultaneous transmittingand receiving system, and injecting the digital cancellation signalupstream from the receiving element to eliminate saturation from atleast one of the high-power response signal and the receiving line,wherein the high-power transmission signal and the high-power responsesignal have a power level ranging from approximately 60 power decibels(dBm) to approximately 80 dBm.
 10. The method of claim 9, furthercomprising phase-shifting the cancellation signal with respect to thehigh-power transmission signal.
 11. The method of claim 10, furthercomprising combining the cancellation signal to the high-power responsesignal such that saturation of the high-power response signal iseliminated.
 12. The method of claim 11, further comprising identifying atype of saturation among a plurality of different saturation types, andgenerating the cancellation signal in response to identifying the typeof saturation.
 13. The method of claim 12, further comprising deliveringthe cancellation signal to receiving line prior to outputting thetransmission signal.
 14. The method of claim 13, further comprisingphase-shifting the cancellation signal 180 degrees with respect to thetransmission signal.
 15. The method of claim 9, further comprising:modeling a signal leakage path that exists between the first antenna andthe second antenna; and generating the cancellation signal based on themodeled leakage path.